Stiripentol (STP), also called 4-dimethyl-1-[(3,4-methylenedioxy)-phenyl]-1-penten-3-ol, is the compound of the formula:

Stiripentol belongs to the family of α-ethylene alcohols which act on the central nervous system. It is capable of treating diseases of the central nervous system and is especially used as a medicament (called Diacomit®) for its anti-epileptic effect, for example in patients suffering from severe myoclonic epilepsy in infancy.
Diacomit® is presented in the form of gelatin capsules containing 250 mg or 500 mg of stiripentol or in the form of granules for a drinkable suspension in a 250 or 500 mg sachet. The particle size distribution of the stiripentol contained in these formulations is such that the diameter of 50% (by number) of the particles (hereinafter denoted d50) is less than or equal to 100 μm, especially from 50 to 85 μm, and the diameter of 90% (by number) of the particles (hereinafter denoted d90) is less than or equal to 300 μm, especially less than or equal to 250 μm.
These particles can be obtained in accordance with conventional grinding and screening processes in order to produce the defined particle size distribution. However, grinding poses problems because, owing to its relatively low melting point (m.p.=75° C.), stiripentol has a tendency to melt in the course of processing, which results in the particles sticking to each other and therefore in major product losses.
Patent FR 7 343 939 describes the crystallization of stiripentol in ethanol. However, there is no indication as to the particle size distribution of the product obtained. Furthermore, since stiripentol is very soluble in ethanol at ambient temperature, this crystallization process is difficult to transfer to an industrial scale.
A process has now been found which enables stiripentol particles having the desired particle size distribution to be prepared, with good yields, and which can be carried out on an industrial scale. To be more precise, it has been shown that, by effecting recrystallization of stiripentol from an aromatic solvent, it is possible to obtain the desired particle size distribution directly, without subsequent grinding and/or screening steps. In addition, this process enables a product of high purity to be obtained.